Electrospinning is a common conventional process for fabricating polymeric fibers. Electrospinning uses high voltages to create an electric field between a droplet of polymer solution at the tip of a needle and a collection device. One electrode of the voltage source is placed in the solution and the other electrode is connected to the collection device. This exerts an electrostatic force on the droplet of polymer solution. As the voltage is increased, the electric field intensifies, thus increasing the magnitude of the force on the pendant droplet of polymer solution at the tip of the needle. The increasing electrostatic force acts in a direction opposing the surface tension of the droplet and causes the droplet to elongate, forming a conical shape known as a Taylor cone. When the electrostatic force overcomes the surface tension of the droplet, a charged continuous jet of polymer solution is ejected from the cone. The jet of polymer solution accelerates towards the collection device, whipping and bending wildly. As the solution moves away from the needle and toward the collection device, the jet rapidly thins and dries as the solvent evaporates. On the surface of the grounded collection device, a non-woven mat of randomly oriented solid polymeric fibers is deposited. Zufan (2005) Final RET Report; Xie, J. W. et al. (2008) Macromolecular Rapid Communications 29(22):1775-1792; Reneker, D. H., et al. (2007) Advances in Applied Mechanics 41:43-195; Dzenis, Y. (2004) Science 304(5679):1917-1919; Rutledge, G. C. and Yu, J. H. (2007) “Electrospinning” In Encyclopedia of Polymer Science and Technology, John Wiley & Sons: New Jersey; Krogman, K. C., et al. (2009) Nature Materials 8(6):512-518; Pham, Q. P., et al. (2006) Tissue Engineering 12(5):1197-1211; Boland, E. D., et al. (2001) Journal of Macromolecular Science—Pure and Applied Chemistry 38(12):1231-1243; Teo, W. E. and Ramakrishna, S. (2006) Nanotechnology 17(14):R89-R106; Li, D.; Xia, Y. N. (2004) Advanced Materials 16(14):1151-1170; Greiner, A. and Wendorff, J. H. (2007) Angewandte Chemie—International Edition 46(30):5670-5703.
There are multiple drawbacks associated with electrospinning, e.g., a low production rate, the requirement of a high voltage electrical field, the requirement of precise solution conductivity, and the need for additional devices for producing aligned fiber structures. Lia and Xia (2004) Advanced Materials 16:1151-1170; Weitz, et al. (2008) Nano Letters 8:1187-1191; Arumuganathar, S. and Jayasinghe, S. N. (2008) Biomacromolecules 9(3):759-766.
Devices and methods to overcome the drawbacks associated with electrospinning have been described in, for example, U.S. Patent Publication No U.S. 2012/0135448 and PCT Publication No. WO 2012/068402. These devices are referred to as Rotary Jet Spinning Devices (RJS) and allow the facile fabrication of polymeric fibers having micron, submicron, and nanometer dimensions. RJS devices permit the formation of polymeric fibers by essentially ejecting a polymer solution through an orifice of a reservoir into air. Air drag extends and elongates the jets into fibers as the solvent in the material solution rapidly evaporates. Nonetheless, in the case of slow evaporating solvents, e.g., aqueous solvents, and in the case of reservoirs that spin at low rotational speeds, the air drag experienced by the material jets may not be sufficient to evaporate certain solvents before they reach the collection device. In addition, air drag alone is insufficient to prepare polymeric fibers in the case of polymers that require on-contact crosslinking, precipitation, and/or a combination of elongation in air and on-contact crosslinking or precipitation. Therefore, fabrication of polymeric fibers using water soluble polymers and/or polymer solutions which, e.g., require on-contact crosslinking and/or precipitation, to form physically and chemically stable polymeric fibers remains challenging.
Accordingly, there is a need in the art for improved systems, devices and methods for the fabrication of polymeric fibers, such as nanofibers.